This invention relates to an antistatic composition for use in a label construction, and more particularly, to an antistatic composition which may be applied to a substrate in a label construction which provides antistatic properties to the label without interfering with high print quality.
Film label constructions are widely used in the art. Such label constructions typically comprise a polyester film which is printed on one surface and a pressure sensitive adhesive on the opposite surface. Typically, the adhesive is covered with a release liner. A disadvantage of such label constructions is that the use of polyester films results in the accumulation of static electrical charges on the films. Such charges are often generated when the labels are provided in direct contact with one another such as in the form of a stack or a roll. The generation of static charges is also affected by the conductivity of the film material and the conditions under which the material is handled. The build-up of static charges causes many problems during printing of the labels, including the attraction of dust and debris to the film, causing poor print quality. In sheet-fed non-impact printers, the static charges often cause sheets to stick together, resulting in skewing, double-feeding, and jams in the printer. When printing polyester labels in roll form, build-up of static charges can cause print quality to deteriorate or even cause the printer to shut down.
To reduce or eliminate the adverse effects resulting from the accumulation of static charges, many label manufacturers apply an antistatic coating to the surface of the film layer. However, such antistatic coatings can interfere with the ability of the film to accept toner images, resulting in poor print quality because of toner bonding problems. While toner-bond enhancement coatings are known which may be applied to the film to increase adhesion of printed images to the film, such toner-bond enhancement coatings often negate the effectiveness of the antistatic coating.
Accordingly, there is still a need in the art for an antistatic coating which may be used on film label constructions which eliminates static build-up while not adversely affecting images to be printed on the film with adequate toner adhesion.
The present invention meets that need by providing an antistatic composition for use with a film label construction which eliminates the problem of static build-up. The antistatic composition is preferably applied to the release liner in the construction. Optionally, the antistatic composition is applied in combination with a toner adhesion-enhancing coating which is applied to the film layer so as to provide high quality print quality without adversely affecting the properties of the antistatic composition. The resulting reduction in static electricity build-up eliminates mis-feeds or double feeding problems when using high-speed sheet-fed printers for processing sheets or rolls of film label constructions.
According to one aspect of the present invention, an antistatic composition for use in a label construction is provided. The antistatic composition comprises an organic cationic polyelectrolyte, a binder, and a surfactant. Preferably, the binder comprises polyvinylpyrrolidone.
In a preferred embodiment of the invention, a label construction is provided comprising a substrate having first and second major surfaces; a pressure sensitive adhesive on the second surface of the substrate; and a release liner having first and second major surfaces which overlies the pressure sensitive adhesive. The substrate preferably comprises polyester. The release liner preferably comprises a cellulosic substrate having a release coating on its first surface.
An antistatic composition is included on the second surface of the release liner, where the antistatic composition comprises an organic cationic polyelectrolyte, a binder, and a surfactant. The antistatic composition reduces the surface resistivity of the second surface of the release liner so as to eliminate static build-up during use of the labels. The second surface of the release liner (including the antistatic composition) preferably has a surface resistivity of less than about 1011 ohm/square and more preferably, about 108 ohm/square.
Preferably, the label construction further includes a toner adhesion-enhancing coating on the first surface of the substrate which provides enhanced adhesion of toner images printed on the substrate.
In an alternative embodiment of the invention, a continuous series of labels is provided comprising a web having first and second major surfaces and having a series of individual labels thereon. A pressure sensitive adhesive is included on the second surface of the web, with a release liner having first and second major surfaces overlying the pressure sensitive adhesive. An antistatic composition is included on the second surface of the release liner comprising an organic cationic polyelectrolyte, a binder, and a surfactant. In this embodiment, the web preferably comprises polyester and is in the form of a roll.
In another alternative embodiment of the invention, a stack of individual labels is provided, where each individual label comprises a substrate having first and second major surfaces, a pressure sensitive adhesive is on the second surface of the substrate; and a release liner having first and second major surfaces overlies the pressure sensitive adhesive. An antistatic composition is included on the second surface of the release liner such that the antistatic composition on the release liner of one label in the stack contacts the surface of an adjacent label in the stack. In this embodiment, the antistatic composition also reduces the coefficient of friction between adjacent labels in the stack.
Accordingly, it is a feature of the present invention to provide an antistatic composition for use in a label construction which reduces the build-up of static electricity. It is also a feature of the present invention to provide an antistatic composition which reduces the build-up of static electricity in a stack or roll of labels. It is a further feature of the present invention to provide an antistatic composition which may be used in combination with a toner-adhesion enhancing coating to provide high print quality on a label construction. Other features and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims.